1,527 articles
Hypomyelination with brain stem and spinal cord involvement and leg spasticity
HBSL (hypomyelination with brain stem and spinal cord involvement and leg spasticity), also called aspartyl-tRNA synthetase deficiency, is an autosomal recessive DARS1 leukodystrophy causing leg spasticity, nystagmus, and hypomyelination on MRI.
Hypopyon
Hypopyon (anterior chamber pus level, ICD-11 MC20.2) is a gravity-dependent layer of white blood cells in the eye's anterior chamber, signaling severe intraocular inflammation from causes such as HLA-B27 uveitis, Behçet disease, endophthalmitis, and keratitis.
Hypotonia
Hypotonia (decreased muscle tone, floppy infant syndrome) is abnormally low resistance to passive movement, distinct from weakness. Causes are central (60-80% of neonatal cases) or peripheral neuromuscular; evaluation uses clinical signs and targeted testing.
Idiopathic bilateral vestibulopathy
Idiopathic bilateral vestibulopathy (IBV, ORPHA 171684) is an acquired bilateral peripheral vestibular dysfunction of unknown cause, with persistent unsteadiness and oscillopsia but no hearing loss beyond age-related; first defined by Baloh et al. in 1989.
Idiopathic hypersomnia
Idiopathic hypersomnia (IH), a chronic central disorder of hypersomnolence, causes excessive daytime sleepiness, long unrefreshing sleep, and sleep drunkenness without cataplexy; cause unknown, diagnosed by MSLT and 24-hour sleep time, treated with oxybate and stimulants.
Idiopathic intracranial hypertension
Idiopathic intracranial hypertension (IIH, pseudotumor cerebri) is raised intracranial pressure of unknown cause, mainly in obese women of reproductive age, diagnosed by modified Dandy criteria and treated with weight loss and acetazolamide.
Idiopathic macular telangiectasia type 1
Idiopathic macular telangiectasia type 1 (MacTel type 1, aneurysmal telangiectasia) is a rare unilateral retinal disease of middle-aged men with parafoveal capillary dilation, aneurysms, and macular edema; laser photocoagulation is the mainstay, dexamethasone implants outperform anti-VEGF.
Idiopathic optic perineuritis
Idiopathic optic perineuritis (idiopathic OPN), also called primary perioptic neuritis, is a rare orbital inflammatory disease targeting the optic nerve sheath, causing painful vision loss over weeks, perioptic MRI enhancement, steroid responsiveness, and relapse risk, without multiple sclerosis association.
Idiopathic orbital inflammation syndrome
Idiopathic orbital inflammation syndrome, also called nonspecific orbital inflammation or orbital pseudotumor, is a benign noninfectious orbital inflammation diagnosed by exclusion, treated first with systemic corticosteroids.
Idiopathic panuveitis
Idiopathic panuveitis, also called idiopathic panuveitis of unknown etiology, is a rare inflammatory eye disease (ORPHA:280921, ICD-10 H44.1) inflaming the entire uvea, retina, and vitreous with no identified cause; treated mainly with corticosteroids and immunosuppressants.
Idiopathic recurrent stupor
Idiopathic recurrent stupor (IRS) is a rare neurologic disorder of sudden unresponsiveness lasting hours to days, identified in Bologna in 1992 and now considered an unproven entity, as some cases were hidden benzodiazepine intoxication.
Idiopathic scleritis
Idiopathic scleritis (ORPHA:648675, ICD-10 H15.0) is painful inflammation of the sclera without infection or systemic autoimmune disease; the most common scleritis category, treated with NSAIDs, corticosteroids, or methotrexate.
Idiopathic uveal effusion syndrome
Idiopathic uveal effusion syndrome (IUES, uveal effusion syndrome type 3) is a rare acquired eye disease with suprachoroidal fluid causing ciliochoroidal and exudative retinal detachment, diagnosed by exclusion, treated mainly by sclerectomy.
Immune effector cell-associated neurotoxicity syndrome
Immune effector cell-associated neurotoxicity syndrome (ICANS) is a potentially life-threatening neurological side effect, most common after CAR T-cell therapy, causing aphasia, confusion, seizures, and cerebral edema treated with corticosteroids.
Immune-mediated scleritis
Immune-mediated scleritis (ORPHA:648681, ICD-10 H15.0) is a rare, severe scleral inflammation linked to systemic autoimmune disease, most often rheumatoid arthritis or granulomatosis with polyangiitis, typically granulomatous or necrotizing and treated with NSAIDs, corticosteroids, and immunosuppressives.
Impacted cerumen
Impacted cerumen (earwax blockage, ICD-11 AA42, ICD-10 H61.2): wax accumulation causing symptoms or blocking ear examination; affects 10% of children, 5% of adults; treated with cerumenolytics, irrigation, or manual removal.
Impairment of colour vision
Impairment of color vision, commonly called color blindness or color vision deficiency, is a reduced ability to distinguish colors, affecting about 8% of males and often inherited.
Impairment of visual field
Impairment of visual field (ICD-11 9D41) is partial or total loss of the area seen with fixed gaze, caused by glaucoma, stroke, retinal disease; measured by perimetry, affecting driving and mobility.
Inappropriate saccades
Inappropriate saccades (saccadic intrusions and oscillations, ICD-11 9C85.02) are involuntary conjugate fast eye movements that interrupt fixation. Types include square wave jerks, ocular flutter, and opsoclonus, linked to neurologic and paraneoplastic disease.
Increased cerebrospinal fluid production
Increased cerebrospinal fluid production (ICD-11 8D64.00), overproduction of CSF by the choroid plexus, chiefly in choroid plexus papilloma, causing communicating hydrocephalus; documented outputs up to 5 L/day.
Increased energy
Increased energy (ICD-11 MB22.4) is a symptom of unusually high felt energy availability, seen in manic and hypomanic episodes and in thyrotoxicosis, and distinct from fatigue as a separate construct.
Infant-type hemispheric glioma
Infant-type hemispheric glioma (IHG), a 2021 WHO CNS5 entity, is a high-grade RTK fusion-driven (ALK, NTRK, ROS1, MET) cerebral hemispheric glioma of infancy, ungraded, treated with surgery plus chemotherapy.
Infantile cerebellar-retinal degeneration
Infantile cerebellar-retinal degeneration (ICRD, OMIM 614559) is an ultrarare autosomal recessive ACO2-related neurometabolic disorder with onset at 2-6 months of hypotonia, ataxia, seizures, optic atrophy, and retinal degeneration.
Infantile dystonia-parkinsonism
Infantile dystonia-parkinsonism, or dopamine transporter deficiency syndrome (DTDS, PKDYS), a rare autosomal recessive SLC6A3 movement disorder causing infantile parkinsonism-dystonia with raised CSF homovanillic acid.
Infantile epileptic spasms syndrome
Infantile epileptic spasms syndrome (IESS), formerly infantile spasms or West syndrome, is an infantile developmental and epileptic encephalopathy with spasms, hypsarrhythmia, and electrodecrement, treated with ACTH, prednisolone, or vigabatrin.
Infantile epileptic-dyskinetic encephalopathy
Infantile epileptic-dyskinetic encephalopathy (IEDE, OMIM 308350, ORPHA 364063), also called X-linked infantile spasm syndrome or EIEE1, is a rare ARX-related, X-linked recessive disorder with infantile spasms, dystonia, status dystonicus, and severe intellectual disability.
Infantile multisystem neurologic-endocrine-pancreatic disease
Infantile multisystem neurologic-endocrine-pancreatic disease (IMNEPD) is a rare autosomal recessive syndrome caused by PTRH2 mutations, combining developmental delay, intellectual disability, ataxia, sensorineural hearing loss, and pancreatic insufficiency, with onset in infancy.
Infantile-onset ascending hereditary spastic paralysis
Infantile-onset ascending hereditary spastic paralysis (IAHSP), also called infantile-onset ascending hereditary spastic paraplegia, is a rare autosomal recessive ALS2-gene motor neuron disorder: leg spasticity begins before age 2 and ascends to arms, speech, and swallowing, sparing intelligence.
Infantile-onset autosomal recessive nonprogressive cerebellar ataxia
Infantile-onset autosomal recessive nonprogressive cerebellar ataxia (SCAR6, OMIM 608029) is a rare recessive ataxia beginning in infancy, nonprogressive, with hypotonia, dysarthria, vermis atrophy, locus 20q11-q13; distinct from dominant CACNA1A SCA6.
Infantile-onset spinocerebellar ataxia
Infantile-onset spinocerebellar ataxia (IOSCA, Ohaha syndrome, MTDPS7, OMIM 271245) is a rare autosomal recessive mitochondrial neurodegenerative disease caused by TWNK/C10orf2 Twinkle helicase mutations, mainly the Finnish founder c.1523A>G (p.Y508C) variant, causing ataxia, hypotonia, athetosis, deafness, and often fatal epilepsy.